The most comprehensive studies on a plant lysozyme (EC 3.2.1.17) are those
on the enzyme from papaya (Carica papaya) latex, published in 1967 and 1969
. However, the N-terminal amino acid sequence of five amino acid sequence o
f this enzyme, determined by manual Edman degradation, did not allow assign
ment to any of the much later-classified families of glycosyl hydrolases. N
-Terminal sequence analysis of 22 residues of papaya lysozyme now shows una
mbiguously that the enzyme belongs to the family 19 chitinases. It has prop
erties similar to those of basic class I chitinases with lysozyme activity,
such as cleavage specificity at the C-1 of N-acetylmuramic acid with inver
sion of configuration, but as it lacks an N-terminal hevein domain, it shou
ld be classified as a class II chitinase.